1. Field of the Invention
The present invention relates to a device enabling the state of an apparatus to be determined, and in particular the open or closed state of an electrical cut-out apparatus such as a circuit breaker or a section switch, with the state being determined by means of auxiliary contacts.
2. Description of the Prior Art
It is recalled that an auxiliary contact is a device which, when used with a cut-out apparatus, includes an element that is linked to the movable portion of the cut-out apparatus and that provides a signal which depends on the position of said movable portion. This signal may be a binary signal, e.g. "1" when the apparatus is "in position" (open or closed), and "0" when the apparatus leaves its position. It is also known that auxiliary contacts can be used for suitably driving coils for controlling the opening and the closing of the electrical cut-out apparatus.
The use of an auxiliary contact for remotely determining the position of a circuit breaker can include the risk of error. An auxiliary contact is a device that may decay: it does little, and its metal contacts may become covered in a layer of oxide. Under such circumstances, the auxiliary contact can provide a wrong signal and can lead to a decision being taken to open a section switch when a circuit breaker that is believed to be open is in fact still closed.
Attempts have therefore been made to improve the operating safety of auxiliary contacts by using redundancy.
For example, two auxiliary contacts are installed instead of one, and the signal provided by each of them is received by an OR type circuit, such that the signal taken into account is that given by the output from the OR circuit.
It is observed that when indicating that the apparatus is "in position", it suffices that one or other of the two auxiliary contacts still gives a "1". If P is the probability of a breakdown in a signal contact, the probability of giving a wrong "in position" signal is P.times.P. To indicate that the apparatus is "out of position", the two auxiliary contacts must both give a "0" signal, thus the probability of giving a wrong "out of position" signal becomes 2P.
It can thus be seen that passive redundancy using two auxiliary contacts does not give the same results for the two signals expected from the auxiliary contact, and, finally, this technique does not solve the problem posed.
Proposals have been made to use passive redundancy with three auxiliary contacts and with a two-out-of-three majority decision being taken.
To give a "in position" signal, it suffices that two of the auxiliary contacts should be giving a "1" signal. The acceptable combinations for transmitting a "in position" are thus:
1 1 1 PA1 1 0 1 PA1 0 1 1 PA1 1 1 0 PA1 0 0 0 PA1 0 0 1 PA1 1 0 0 PA1 0 1 0 PA1 when "in position" the reading will be 111, and that is correct; but PA1 if an auxiliary contact changes state without a state changing instruction being issued by the microcontroller, then the microcontroller considers that the auxiliary contact is faulty and no longer takes its signals into account; and PA1 if after a change of state instruction has been issued by the microcontroller an auxiliary contact does not change state in a given time delay, then the microcontroller considers it to be faulty and does not take signals from it into account; PA1 the software also taking account of the states of good auxiliary contacts as they appear at the instant when a change of state instruction is issued, and the change of state instruction itself. PA1 an auxiliary contact which does not change state within a given time delay following an open or a close instruction is considered as being faulty and is no longer taken into consideration by the program; PA1 an apparatus is declared to be opened at the end of an open sequence if one of the following situations occurs at the end of said opening sequence: PA1 an apparatus is declared to be closed at the end of the close sequence if one of the following circumstances arises at the end of said closed sequence: PA1 the program also being organized so that: PA1 a group of contacts is declared faulty (a major auxiliary contact group failure corresponding to an MFCA=1 signal) if none of the auxiliary contacts of the group has changed state during a first time delay (TIME0) following an instruction to open or close the apparatus, and while during the same time lapse an appropriate change is observed for the auxiliary contacts of the other group; and PA1 an auxiliary contact is declared faulty if it has not changed state at the end of a second time delay (TIME1), initiated by another auxiliary contact of the same group changing state appropriately during an open sequence or a close sequence of the apparatus. PA1 the n open auxiliary contacts are good and in the "1" state if all of the closed auxiliary contacts are faulty; and PA1 the n closed auxiliary contacts are good and in the "0" state if all the closed auxiliary contacts are faulty. PA1 at least one closed auxiliary contact is good and in the "1" state; and PA1 at least one of the open auxiliary contacts is good and in the "0" state. PA1 when an open or a close instruction (OO, OF) is given at time origin (t0), a first surveillance time window having a first duration (TIME0) is initiated by a first time delay (TEMPO1), and simultaneously a first timer (CHRO0) is started; PA1 when the first of the auxiliary contacts of a first group changes state (an open auxiliary contact for an open instruction or a closed auxiliary contact for a close instruction) at an instant t1, a second time window having a second duration (TIME1) is opened by means of a second time delay (TEMPO1) and simultaneously the first timer (CHRO0) is stopped, the time it provides is stored in memory, which time corresponds to the starting time from rest, and a second timer (CHR1) is started; PA1 at the end of the second time duration (TIME1), at instant t2, the auxiliary contacts of said first group have had the chance to change state, and the resulting states thereof are stored in order to be analyzed; PA1 when the first signal contact of the second group changes state at instant t3, said second time window of the second duration (TIME1) is started again using said second time delay (TEMPO1) and simultaneously the second timer (CHR1) is stopped and the time it provides is stored and is suitable for use in determining the mean speed of the contacts of the equipment; PA1 when the second time delay expires (TIME1), all of the good auxiliary contacts in the second group will have changed state, and the resulting states are stored in order to be analyzed; PA1 an auxiliary contact in the first group or in the second group is declared to be faulty if it has not changed state at the end of the second time window (TIME1) relating thereto; and PA1 a group of auxiliary contacts is declared to be suffering from a major fault if none of the auxiliary contacts in the group has changed state by the end of the first time window (TIME0) when an appropriate change of state has been observed in the opposite group. PA1 during an apparatus opening process, after observing that the sequence has been initiated by a change in the state of a closed auxiliary contact and that none of the open auxiliary contacts has changed state at the end of the first time window (TIME0), causes an apparatus fault signal (MFP=1) to appear; PA1 during an apparatus opening process, after observing that the sequence has not been initiated because none of the closed auxiliary contacts has changed state at the end of the first time window, causes an "apparatus open" signal (PO=1) to appear if all three open auxiliary contacts have not changed state, and simultaneously issues a major fault signal concerning the closed auxiliary contacts (MACAF=1, MFCA=1); PA1 during an apparatus opening process, after observing that the sequence has not been initiated because none of the closed auxiliary contacts has changed state at the end of the first time window, and having observed no change of state in the good open auxiliary contacts, causes an apparatus failure signal (MFP=1) to appear and locks out any subsequent instruction; PA1 during an apparatus closing process, after observing that the sequence has been initiated by an open auxiliary contact changing state and observing that none of the closed auxiliary contacts has changed state at the end of the first time window (TIME0), causes an "apparatus closed" signal to appear, with the second duration being taken to be equal to the duration of the first time window (TIME0); PA1 during an apparatus closing process, after observing a major fault of the closed auxiliary contacts, causes an "apparatus closed" signal to appear if one of the open auxiliary contacts changes state; PA1 during an apparatus closing process, after observing a major fault of the closed auxiliary contacts, and after observing that none of the good open auxiliary contacts has changed state, declares the apparatus to be faulty, takes the first duration (T1) to be equal to the duration of the first time window (TIME0), takes the second duration (T2) to be equal to the maximum capacity of said third timer (FFFF), and causes a third fault mode program (fault mode 3) to be run. PA1 the last recorded given instruction being an open instruction, the device confirms the "apparatus open" state only if at least all of the auxiliary contacts in one of the groups are good; PA1 the last recorded given instruction being a close instruction, the device indicates that the apparatus is closed if at least one good closed auxiliary contact is in the "1" state or if at least one good open auxiliary contact is in the "0" state; and PA1 if all of the open auxiliary contacts and all of the closed auxiliary contacts are faulty, the device indicates that the apparatus is faulty and prevents any subsequent operation thereof.
To give a "out of position" signal, it suffices that two of the auxiliary contacts should be giving a "0" signal. Acceptable combinations for transmitting a "out of position" signal are thus as follows:
Since the probability of two auxiliary contacts failing simultaneously is P.times.P, the same reliability is obtained for the "in position" signal as for the "out of position" signal, namely P.times.P, however this applies so long as only one of the auxiliary contacts is faulty.
In contrast, in the event of a second breakdown, assuming that a first breakdown has not been repaired in the meanwhile, erroneous conclusions may be deduced. For example, if two auxiliary contacts are stuck in the "1" position, then:
when "out of position", the reading will be 110, and that is incorrect since a two-out-of-three majority decision will give rise to a "in position" signal being understood.
It can be seen that the above-described passive redundancy greatly improves the availability of signalling, but that it does this in a manner that is often unsatisfactory given the robustness targets set for the system in the event of multiple breakdowns.
The problem thus remains of monitoring electrical apparatuses remotely and of being able to rely on the signals delivered by auxiliary contacts so as to be able to take operating decisions for a grid without taking risks.
An object of the invention is thus to define a device for determining the position of an apparatus by using auxiliary contacts and making it possible to provide signals that are reliable even when some of the auxiliary contacts are faulty. Under some operating conditions of a grid, e.g. under extreme climatic conditions, it is not always possible to repair an auxiliary contact that has become faulty. It is nevertheless essential to be able to discover the position of the apparatus without risk of error. The device must also ensure proper control of the actuators of the apparatus.
Another object of the invention is to define a device that is capable of providing signals enabling it to diagnose itself, in particular signals specifying the good or faulty state of the auxiliary contacts in the apparatus. The availability of the apparatus is thus increased by enabling maintenance to be performed thereon in knowledge of the facts.
Another object of the invention is to define a device making it possible to improve knowledge about the electrical apparatus used while it is being used, for example if the apparatus is a circuit breaker, making it possible to learn how long it takes to operate. One such duration may be the time that elapses between the beginning of an instruction being given to the circuit breaker and the circuit breaker moving from its starting position. Another duration may be the time that elapses between starting from a given position and arriving in the opposite position. Knowledge of such operating times makes it possible to improve maintenance of the apparatus and to forestall major breakdowns.